In this episode, Bob and Mike discuss water reactive stuff and what it means to us.
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• water reactive
• why do these react
– reactions can happen for a variety of reasons. But it all comes down to the fact that the overall energy of the system will be lower if it reacts with water or even sometimes just air.
– although as a side not a lot of air reactive things are reacting with the moisture. Some are reacting with the O2 but some can be moisture in the air.
– Weather were are sharing electrons or trying to find a lower energy state the basic is that two chemicals that want to react came together. And for us, its is in a situation where they are doing it in an uncontrolled manner.
• How do we determine if a substance is water reactive?
• section 5, fire and explosion data
• green pages
– sometime nomenclature can give away water reactive possibility
• Alkali metals
• acyl chlorides
• main group metal halides
• metal oxides
• acid anhydrides
• Nonmetal oxides
– ok so cool note. Co2 is a nonmetal oxide. And it does, in fact, react with water. however this reaction in not very exothermic so it doesn’t give off a lot of energy. therefore we consider it to be compatible.
– Which is why these nomenclatures are guides, not rules. they should make you stop and pause, do some research before proceeding forward.
• the reverse is true, just because something doesn’t fall into one of these nomenclature categories doesn’t mean it can’t be water reactive.
– types of water reactive outcome
• flammable gas
– products that in the presence of water give off a gas that is flammable.
• Calcium carbide and water is the most common example. When these two come together they create an extremely flammable gas called ethyne. AKA Acetylene.
• beryllium carbide and water will produce methane
• Calcium hydride and water produces hydrogen gas
– so the hazards is not a thermal reaction to water. It doesn’t blow up or produce a fire. But it can give off a gas that can produce a dangerous atmosphere.
– So what our options for this. if water and the product have mix what do we do
• need to determine what the product is. Remember the hazard is now the product, not the original chemical
• acts as we would with any other flammable gas
– determine if the reaction is done. if not can i stop it
– where is the gas going, up or down
– do have ignition sources
– can i ventilate
– can i meter
• toxic gasses
– Our next section are chemicals that react to form a toxic or irritating gas
• some metals that are paired with nitrogen will produce ammonia
– Lithium nitride
• other types produce even more extreme toxic substance like Phosphine gas. Which is produced when aluminum phosphide comes into contact with water
• I personally think that as a first responder this is the easiest to protect myself from.
– most of the toxic like ammonia but i can protect myself with my scba. Very few things are going to really be toxic as a skin absorbable
– So if i can protect myself with SCBA what is my concern
• Going to make sure people without scba are safe
try to determine what the product is
this will allow me to determine how to meter for this
PID, FID, Drager tubes and chips
why would you go with a drager tube
first it is going to depend on the area. i would use this for inside. I want to really make sure that the area is safe for others.
• determine the extent of the reaction
so here size matters on this one why?
how much product as come in contact with how much water
how long is it going to keep going
• Can i separate unreacted product
• Can I provide a safe ventilation?
why safe, because i need to know where i am pushing this toxic material
• when a water reactive material creates a corrosive it can produce one of two things. a gas or a solutions.
– Last but not least is thermal. This is when the material that comes in contact with water produces a violent reaction with the water.
• This really comes in two forms.
– The product can catch on fire.
• As a hazmat responder i don’t think this is much of an issue for us. We going to get called after this reaction happens. In fact the fire department is going to go for the fire.
Yes, most of the reagents are going to be eaten up by the fire
ya but that’s assuming small quantity. What if we have a large quantity with a small leak. Like a gas that is leaking that is igniting.
Thats a good point. So here the problem. we need water to cool the container.
• metal in a lab
– Called to a college lab, where a student has drop a glass jar with a reactive metal in it. You arrive on scene. from Recon video taken via robot you see a broken glass, a viscous fluid and chuck of substance that is obviously reacting. what you doing.